Make your own free website on Tripod.com
Yale C/AIM Web Style Guide

Contents

Web Graphics

Introduction

Color display primer

Graphic file formats

Interlaced GIF

Transparent GIF

JPEG graphics

Summary-File formats

Illustrations

Optimizing graphics I

Optimizing graphics II

Height & width tags

Colored backgrounds

Imagemaps

Web background colors offer a "zero-bandwidth" means to change the look of your pages without adding graphics. They also allow you to increase the legibility of your pages, tune the background color to complement foreground art, and to signal a broad change in context from one part of your site to another.
Background patterns and background images are the most controversial graphic elements on Web pages. Both features add graphic complexity to pages without increasing their legibility. Poor choice of background graphics has generated some of the ugliest pages on the Web. However, in the hands of experienced and knowledgeable graphic designers the use of these background features can result in Web pages as stunning in graphic impact as anything seen in multimedia CD-ROMs.

Changing the colors of page elements
Netscape allows you to specify a specific color for the background, text, and hypertext links of your Web page, making it possible to get rid of the default gray or white background without having to download big graphics. You can also manipulate the colors of other page elements in web pages, using a simple set of HTML extensions. These extensions may be the most efficient way to give your pages a distinctive look, because the browser handles all of the color changes, and your readers do not have to sit still while you download fancy graphics to them.
Picking the background color is easy in WYSIWYG (what you see is what you get) graphic web page layout programs. Unfortunately, picking a color without one of these Web page editors is a procedure only a gearhead could love. The color is specified in the tag in hexadecimal code, where the six elements give the red, green, and blue values that blend to make the color. In the tag, the hex code is always preceded by a "#" sign: (#RRGGBB). Since this whole business is handled visually by the new generation of WYSIWYG page editors, we will not go into further details on the arcana of hexadecimal RGB color selection.

Here are hex color codes for some background colors:

Background color swatches.

Using the HTML extensions for changing the color of page backgrounds, text, and link colors is easy you just add a few extensions to the "BODY" tag at the beginning of your HTML code for the page (this particular tag yields a white background):

<BODY BGCOLOR="#FFFFFF">

Background colors and legibility
Shifting the page background from gray to white is really the only alteration of the standard Web page background that we can recommend if your highest priority is screen legibility. The legibility of type on the computer screen is already compromised by the low resolution of the computer screen. The typical Macintosh or Windows computer screen displays text at 72 to 80 dots per inch ( about 5,200 dots per square inch), or almost 300 times less resolution than a typical magazine page (1,440,000 dots per square inch). Black text on a white (or very light gray) background yields the best overall type contrast and legibility. Studies have shown the black backgrounds are significantly less legible than white backgrounds, even when white type is used (for maximum contrast). Colored backgrounds can work as an alternative to plain Netscape gray if the colors are kept in very muted tones, and low in overall color saturation (pastels, light grays, and light earth tones work best).

Netscape background patterns
Early in 1995 Netscape 1.1N gave Web page authors the ability to use small tiled GIF or JPEG graphics (or a single large graphic) to form a background pattern behind the Web page. The feature is controversial in Web design discussions, because pages that use large background images take much longer to download, and because the background patterns tend to make pages much harder to read unless they are carefully designed:

Example of legibility problems with background patterns.

To be suitable for use as a texture the graphic should be a small GIF or JPEG, ideally no more than about 100 by 100 pixels in size. In our experience, the JPEG background patterns load slightly faster than equivalent GIF graphics. Typical graphics used for background patterns are homogeneous textures:

Examples of background patterns.

Background graphics are added to a Web page by Netscape-specific modifications of the standard "BODY" HTML tag:
<BODY BACKGROUND="example.jpeg">
When Netscape sees the BACKGROUND tag it will tile the graphic file "example.jpeg" across the page, under the text and any other graphics. Older Web browsers that do not support background images will just ignore the background tag, and give the page a default white or gray background.
How you might use background textures depends entirely on your goals for your Web site, the access speeds that are typical for your target audience, and whether the multimedia/CD-ROM style look (fast becoming a cliche) meets the aesthetic goals of your Web site. Using large or visually complex background textures on any page that is heavily accessed by busy people looking for work-related information would be foolish the long download times, unprofessional aesthetics, and poor legibility would instantly create ill will in your users. However, in the hands of skilled graphic designers creating Web pages specifically designed for graphic impact, the option to use background textures opens up many interesting visual design possibilities. This is particularly true in universities and commercial organizations where fast network access is commonplace and bandwidth is not the major issue it is with modem-based users.
Our advice is: if you don't have professional graphic design training or experience in constructing complex graphic communications, then stay away from background images or textures the chances making a bad functional and aesthetic mistake are overwhelming.
Copyright 1997 P. Lynch and S. Horton,